4.1 The Parser Function yyparse

You call the function yyparse to cause parsing to occur. This
function reads tokens, executes actions, and ultimately returns when it
encounters end-of-input or an unrecoverable syntax error. You can also
write an action which directs yyparse to return immediately
without reading further.

Function: intyyparse(void)

The value returned by yyparse is 0 if parsing was successful (return
is due to end-of-input).

The value is 1 if parsing failed because of invalid input, i.e., input
that contains a syntax error or that causes YYABORT to be
invoked.

The value is 2 if parsing failed due to memory exhaustion.

In an action, you can cause immediate return from yyparse by using
these macros:

Macro: YYACCEPT

Return immediately with value 0 (to report success).

Macro: YYABORT

Return immediately with value 1 (to report failure).

If you use a reentrant parser, you can optionally pass additional
parameter information to it in a reentrant way. To do so, use the
declaration %parse-param:

Directive: %parse-param{argument-declaration} …

Declare that one or more
argument-declaration are additional yyparse arguments.
The argument-declaration is used when declaring
functions or prototypes. The last identifier in
argument-declaration must be the argument name.